Volume III, Issue 7, Page 43
The 2-mode full
hybrid is a power-split
system, which requires two
motors. One is used mostly as
a generator; the other as an output
motor. The addition of a second mode to the drive system improves efficiency and reduces the need for exceedingly large electric motors.  The 2-mode full hybrid’s smaller motors are lighter and more easily packaged in the space of a typical vehicle transmission.

We know that it’s much more fun to read about building an affordable 1,000hp pump-gas street engine rather than some boilerplate tech developed for mass-consumption passenger vehicles, but the automotive world is scrambling to keep up with the ever-escalating price of light crude. Some sages are saying we’ll eventually shell $7 for a gallon of gasoline (in Germany, it’s over $9), but when you aren’t in the driver’s seat, you gotta do what you’re told. So this bit of technology seems very pertinent now.

The Tahoe Hybrid doesn’t have a whole lot to do with the (RPO LFA) 6.0L Gen IV engine, either. In fact, the motor is ancillary to this program. It’s really about the drivetrain package and most certainly the new electrically variable transmission (EVT).

To build this profoundly cool piece of engineering, GM used its experience in developing hybrid bus propulsion systems. The Tahoe’s EVT hybrid system blends continuously variable operation (for low-load driving situations) with fixed-gear operation (for high-load conditions such as towing or highway driving). In concert with the 6.0L V8 with Active Fuel Management, this system provides excellent economy and full-size SUV passenger-carrying, cargo-hauling and trailer-towing capabilities. Further, the EVT bolts directly to the standard four-wheel-drive transfer case of gasoline-only models.